1. Field of the Invention
The present invention relates to a screen printing apparatus, and more particularly, to a screen printing apparatus which performs screen printing of cream solder, conductive paste or the like onto a board such as a printed wiring board (PWB), as pre-processing for mounting electronic components on the board.
2. Description of the Background Art
A screen printing apparatus is incorporated into a production line for printed circuit boards (PCBs) to carryout screen printing of conductive paste, or the like, onto a board conveyed from an upstream side. The apparatus then sends the board out to a component mounting apparatus on a downstream side. As disclosed in Japanese Patent Application Laid-Open No. H7-205399, one kind of screen printing apparatus which is used in single lane (single lane refers to a production line in which entry and exit paths for the printing apparatus are respectively formed in one single track) has one printing unit which receives boards one by one to conduct a printing process to each board. The apparatus then transports the printed boards towards a component mounting apparatus.
In the prior art, the production line is often required to be halted at every time of replacing tasks because the single lane needs to conduct replacing tasks (replacing the screen mask, and/or the parameter data) and printing task in a sequential manner. Therefore, through-put could be remarkably worse; particularly it will be worse when the production line conducts so-called small-volume diverse-component production.